It's not the villain that The Da Vinci Code sets it up to be. But it has been a mystery. An inside look at the most controversial group in Catholicism

In early March, Elizabeth Heil, an arts-administration graduate student at Columbia University, was watching previews in a movie theater on Manhattan's Upper West Side when she cracked up inappropriately. The trailer was for the movie The Da Vinci Code, directed by Ron Howard and scheduled to open May 19, and it featured a grim-faced fellow uttering Christ's name repeatedly and then--wham!--whaling away at his already bloodied back with an Inquisition-issue cat-o'-nine-tails. It was not an intentionally funny scene. But Heil, who was familiar with the book on which the movie is based, recognized the figure onscreen as the albino assassin Silas,...